This invention relates to spark generation and timing apparatus for internal combustion engines and particularly to such apparatus for use with engines having existing magneto and ignition coil mounts.
Commercial small engines for sport vehicles such as jet skis and snowmobiles, are produced today having features and performance suited to the average user. Many users, however, desire to improve the performance of their vehicles in an inexpensive and unobtrusive manner. Such improvements include a more energetic spark (hotter spark), longer spark duration, automatic battery connect/disconnect, greater noise immunity at the magnetic-pickup, adjustable maximum rpm limits, automatic rpm limits when the engine overheats, tachometer output and a kill switch for particularized operating environments among other things.
Typically for reasons of manufacturing costs, stock ignition systems deliver electrical charge to engine spark plugs via an ignition coil at energy levels well below component tolerances. Such stock ignition systems also do not usually provide precise control over the resulting spark duration. As a result, the price paid for minimizing manufacturing costs is suboptimal ignition energy and duration which in turn compromises the performance of the internal combustion engine. Although stock ignition systems meet the performance needs of the average user, the need exists for increasing ignition energy to optimal levels and particularly for more precise control over spark duration.
Additionally, it would be desirable to provide adjustable limits on maximum engine speed to keep the engine running within a safe range. Further, when engine operating temperature is detected to be higher than desired, it would be desirable to automatically limit the maximum over-temperature engine speed at a lower level.
A problem that exists in receiving ignition triggering signals from a magnetic-pickup for detecting flywheel tabs is a difficulty in accurately ascertaining the zero crossing of the pickup input voltage. This problem is aggravated for widely varying engine speeds. At slow speeds, the pickup voltage may be only one or two volts triggering at about a 0.5 volt threshold. At fast speeds, the resulting pickup voltage may be well over 10 volts. If the trigger threshold remains at about 0.5 volt, it is likely that the engine will misfire on noise signals at high engine speeds. Accordingly, there exists a need for varying the trigger threshold according to engine speed.
It would be further desirable to provide a kill switch for safety in operating environments which, by their nature, present significant switch and wiring leakages making such kill switches impractical due to the likelihood that unintended switching will occur merely due to the operating environment.
It would be still further desirable to provide a tachometer output for measuring the engine rpm of vehicles whose stock ignition system does not provide tachometer capabilities.
The present invention meets the need for performance improvements and additional features by providing an improved electronic ignition system which conveniently utilizes the existing ignition circuitry of vehicles such as the ignition magneto and coil systems.